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Tesi etd-04262020-121816


Thesis type
Tesi di dottorato di ricerca
Author
MAGI, FRANCESCO
URN
etd-04262020-121816
Title
"Isotope geochemistry of rainfall, thermal and non-thermal waters from the Mt. Amiata area (northern-central Italy)"
Settore scientifico disciplinare
GEO/08
Corso di studi
SCIENZE DELLA TERRA
Supervisors
tutor Prof. Pandeli, Enrico
correlatore Prof. Vaselli, Orlando
correlatore Dott. Doveri, Marco
Parole chiave
  • noble gas isotopes
  • fluid geochemistry
  • stable water isotopes
  • Mt. Amiata
Data inizio appello
30/04/2020;
Consultabilità
Parziale
Data di rilascio
30/04/2023
Riassunto analitico
The Mt. Amiata geothermal area was thoroughly investigated during the last decades by structural, hydrogeological and isotope geochemistry tools. Nevertheless, as a consequence of the highly complex hydrogeological setting of the area, characterized by overlapping water (both cold and hydrothermal) bodies with different chemical features and circulation dynamics, a common agreement among the researchers about their interplays between each other and the geological structures has not been achieved yet.
Moreover, it has to be considered that as due to the simultaneous occurrence of drinkable freshwater resources at shallow depths (Mt. Amiata Significant Groundwater Body-SGB), the most important freshwater reservoir supply of both southern Tuscany and northern Latium regions) and, in contrast, highly saline geothermal fluids charged of high contents of toxic elements at deeper levels, some environmental concern have arisen among the local populations about a possible negative impact produced by the geothermal energy utilization on the shallow aquifer.
In order to constrain and find possible answers to such different topics, a multidisciplinary hydrogeological-isotopic approach was adopted.
Accordingly, the main purposes of this research project were to: i) build up the first LMWL for the Mt. Amiata area, by isotopic analyses of rain water sample; ii) better characterize the shallower hydrogeological environments related to both the cold homonymous volcanic and the regional-carbonate aquifers by computing the average infiltration/recharge altitudes of the main springs and iii) define their hydrogeological dynamics by also using 3H dating; iv) verify the effects on the last decade of the climate change and how the shallow groundwater bodies were affected; v) understand the chemical isotopic relationships existing between the different fluid (liquid and gas) end-members as well as their infiltration and/or migration with respect to the geological structures; vi) assess the water quality of the shallow reservoirs to provide the local authorities with useful hints aimed at managing, to the best of the knowledge, the freshwater resource in Mt. Amiata geothermal area.
Sampling surveys were focused on rainfall and spring waters (that allowed to define the very first local meteoric water line) and gas emissions that were investigated for their relative chemical and isotopic composition. Additionally, the results showed that the gas emissions as well as the thermal waters are strictly related to the deep geothermal systems and a partial hydraulic connection (at least for the gaseous fluids) with the deep-seated source was recognized, although clear evidence of possible interferences with the shallow freshwater resources was not highlighted. It is however to be recommended to further develop this research to obtain additional insights by applying geochemical modeling codes to the shallow aquifer and to add more constrains for achieving a reliable hydrological water budget.
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